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This is a blog about paleontology (the study of the history of life on Earth through the fossil record) with an emphasis on vertebrate paleontology, the study of extinct vertebrates (animals with backbones). The methodology and findings of paleontology will be discussed, as well as related issues such as evolutionary theory. The blogger is a vertebrate paleontologist specializing in the Triassic Period, the Beginning of the Age of Dinosaurs.

My posts are presented as opinion and commentary and do not represent the views of LabSpaces Productions, LLC, my employer, or my educational institution.

In the last two blogs (click here for Part I and Part II), we've been talking about ways of determining the relative ages of sedimentary rocks and fossils (e.g. species A lived some time before species B), without determining their exact numeric ages (in thousands, millions, or billions of years). This is referred to as "relative age dating." If we start applying numeric ages, we are talking about "absolute age dating." The main method by which this is done is called radioisotopic dating. Explaining how radioisotopic dating works is going to require that I hop around a bit between subjects, but it will all come together in the end.

Just to give a little basic physics recap, an atom is made up of three types of particles: protons, neutrons, and electrons. The number of protons determines the type of atom (and element); for example, an atom of potassium (K) always has 19 protons, which is its "atomic number". The number of neutrons only changes the mass of the atom; atoms with the same number of protons but different numbers of neutrons . . . More

In the last blog, I discussed the Law of Superposition. Layers of sedimentary rocks, or strata, are stacked in vertical sequences, with the oldest layers being on the bottom, and getting younger as we go up through the layers. Remember that the study of the sequence of layers of strata is called lithostratigraphy, and the study of the sequence of fossils in these same layers is called biostratigraphy. Both of these studies were pioneered in the early 19th century by a British geologist named William Smith, who was one of the very first to figure out that you could identify the same sequences of rocks and fossils in different parts of England (an excellent book about Smith and his life is The Map That Changed the World by Simon Winchester). Smith was primarily interested in the economic benefits of these observations, and was able to use his knowledge of the sequence of rocks and fossils, and how they were distributed across England, to inform land owners whether or not they could find coal or building stone on their property. What Smith did not fully appreciate during his lifetime was that he had also figured out the primary methods that . . . More

Sorry about the delay since my last post. I've got a series of blogs about the evolution of dinosaurs and closely related reptiles that I want to do, but as I started writing it, I realized that I ought to do a series of blogs giving a little background into how paleontologists know what they know about the history of life first, and also about what exactly dinosaurs are and how they fit into the big picture of life. So, first things first. Also, I AM paying attention to questions that people ask in the comments section, and will try to cover them (eventually).

This first blog is about how we put events in the history of life in order. Imagine a novel being written in collaboration by a bunch of different authors. Some of them are writing about characters, some about settings, some about specific events which occur in the plot...but they are writing in isolation, and no one has any idea how these people, settings, and events are ordered. What happened first? Did the characters go to Paris after their trip to Mars, or before? Did the schizophrenic dog kill his owner before or after his affair with the monkey? This stuff is important. Everyone is just writing their own pages, but until someone takes all the pages and put them in order, there is no story.